能谱CT冠状动脉造影单能量图像质量的优化

Imaging quality optimization of CT coronary angiography by using monochromatic spectral images

目的评估能谱CT冠状动脉造影中不同keV水平单能量图像的客观质量控制参数,确定最佳单能量图像。方法采用能谱CT机对100例受检者进行能谱CT冠状动脉造影,并分为正常组50例,病变组50例。对40~140keV间隔5keV的21组单能量图像噪声（Noise）进行测量,计算正常组和病变组前降支（LAD）、左旋支（LCx）及右冠状动脉（RCA）的SNR和CNR及病变组中242个斑块的CNR。采用单因素方差分析和独立样本t检验评估冠状动脉（LAD、LCx、RCA的近、中、远段）图像的Noise、SNR及CNR。结果单能量图像Noise下降趋势的分界值在60keV,正常组、病变组血管的SNR、CNR值均在40~70keV水平明显高于其他keV水平。60keV水平单能量图像的SNR、CNR值在正常组与病变组之间差异无统计学意义。结论对于正常组和病变组,60~70keV水平的单能量图像能够获得较高的SNR、CNR和较低的图像Noise,可作为能谱CT冠状动脉造影的最佳单能量水平。

Objective To evaluate objective quality indices to determine the optimal monochromatic spectral image levels of CT coronary angiography.Methods Totally 100 patients underwent CT coronary angiography with dual-energy spectral CT scanner.The patients were divided into the normal group（n=50）and the lesion group（n=50）.All the spectral imaging data were reconstruct to monochromatic spectral images from 40 to 140keV in 5keV increments.For 21 groups of monochromatic spectral image,the imaging Noise,SNR,CNR of all coronary arteries（proximal,middle,and distal segments of left anterior descending,left circumflex and right coronary artery）in both groups were compared by using One-Way ANOVA and independent sample t test.Furthermore,the CNR of coronary plaque was calculated in 242 coronary artery segments of lesion group.Results The general trend among two groups showed that the cutting-off value for monochromatic spectral image Noise was 60 keV.The image CNR and SNR of the range from 40 to 70keV were significant higher than the other keV intervals.There were no differences of SNR and CNR between normal and lesion group in 60 keV level.Conclusion Monochromatic spectral images from 60 keV to 70 keV could significantly improve the coronary image quality by raising the CNR and reducing the Noise in both normal and lesion group,and be used as the optimal keV settings for the coronary arteries assessment.